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REESE  LIBRARY 


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UNIVERSITY  OF  CALIFORNIA. 

,  790    . 

JO.   Class  No. 


j  Accession  No. 

i-u-Ti-u-u-u-u-u-u-u-u— 


LABORATORY  EXPERIMENTS 


ON    THE 


CLASS  REACTIONS  AND  IDENTIFICATION 


OF 


ORGANIC  SUBSTANCES. 


BY 

ARTHUR  A.   NOYES,  PH.D., 

ASSOCIATE  PROFESSOR  OF  ORGANIC  CHEMISTRY  IN  THE  MASSACHUSETTS 
INSTITUTE  OF  TECHNOLOGY, 

AND 

SAMUEL   P.   MULLIKEN,   PH.D., 

INSTRUCTOR  IN  ORGANIC  CHEMISTRY  IN  THE  MASSACHUSETTS 

INSTITUTE  OF  TECHNOLOGY. 


SECOND,   rHOTf9&£&££-KtrriSED  EDITION. 


E ASTON,   PA.: 
CHEMICAL  PUBLISHING  Co. 

1898. 


COPYRIGHT,  1897. 
BY  ARTHUR  A.  NOYES  AND  SAMUEL  P.  MULLIKEN. 


PREFACE. 


THIS  collection  of  laboratory  experiments  in  organic 
chemistry  has  been  prepared  especially  for  the  use  of  the 
classes  of  the  Massachusetts  Institute  of  Technology,  as  a 
supplement  to  the  ordinary  course  of  instruction  in  prepar- 
ation work.  The  authors'  experience  has  shown  that  the 
preparation  of  typical  organic  substances  in  accordance 
with  the  plans  followed  in  the  manuals  of  Gattermann, 
Levy,  Fischer,  etc.,  teaches  satisfactorily  the  manipulative 
methods  of  organic  chemistry  and  the  manner  of  execution 
of  the  leading  synthetic  processes,  but  that  it  fails,  to  a 
surprising  extent  in  the  case  of  most  students,  to  give 
a  knowledge  of  the  important  characteristics  of  the  vari- 
ous classes  of  organic  compounds,  and  therefore  of  the 
fundamental  principles  of  the  science.  Unless  the  instruc- 
tor is  continually  on  the  alert,  the  course  of  preparation 
work  becomes  almost  unavoidably  a  routine  following  of 
directions. 

Although  the  primary  purpose  of  the  experiments  here 
described  is  to  illustrate  the  characteristic  reactions  of  or- 
ganic compounds,  their  analytical  significance  is  a  feature 
of  no  slight  importance ;  for,  both  in  research  and  technical 
work,  the  chemist  has  frequent  occasion  to  identify  the  sub- 
stances he  meets  with.  On  this  account,  and  also  because 
it  is  always  desirable  to  make  evident  to  the  student  some 
practical  use  of  the  information  presented  to  him,  the  an- 
alytical side  of  the  experiments  has  been  made  prominent ; 
and  an  important  part  of  the  course  consists  in  the  iden- 
tification of  unknown  compounds  and  the  quantitative  sep- 
aration of  mixtures  by  methods  devised  by  the  student 
himself  with  the  help  of  the  knowledge  gained  from  the 
experiments  with  known  substances. 


4  PREFACE. 

It  is  believed  that  the  entire  omission  of  explanatory 
statements  of  what  occurs  in  the  experiments  will  cultivate 
the  student's  power  of  observation,  and  cause  him  to  con- 
sider more  carefully  the  principle  illustrated  ;  while  the  work 
on  the  identification  and  separation  of  unknown  substances 
will  afford  abundant  opportunity  for  original  thought.  —  It  is 
assumed  that  a  brief  course  of  lectures  on  the  outlines  of  or- 
ganic chemistry  has  preceded  the  laboratory  experiments. 

Owing  to  the  great  importance,  in  the  opinion  of  the 
authors,  of  instruction  of  this  kind,  and  owing  to  the  fact 
that  no  text-book  presenting  it  exists,  it  has  not  seemed 
advisable  to  postpone  the  publication  of  the  general  plan, 
although  it  is  undoubtedly  imperfect  in  many  matters  of 
detail. 

The  authors  desire  to  express  their  indebtedness  to  Dr. 
J.  F.  Norris  for  many  valuable  suggestions,  and  to  Messrs. 
H.  M.  Loomis,  A.  P.  Norris,  and  C.  L.  W.  Pettee,  for  their 
investigations  on  the  applicability  of  many  of  the  important 
tests. 


EXPERIMENTS  ILLUSTRATING  THE  CLASS  REACTIONS  OF 
ORGANIC  COMPOUNDS. 

Introductory  Explanations  and  Directions. 

THE  following  experiments  serve  to  illustrate  some 
of  the  most  important  properties  and  reactions  of  the 
various  classes  of  organic  compounds.  The  results  ob- 
tained are  to  be  regarded  as  characteristic  of  the  whole 
class  as  defined  by  the  heading  above  the  experiment. 
It  must,  however,  be  clearly  understood  that  all  com- 
pounds of  the  class  do  not  give  these  Reactions  with 
equal  facility  —  that,  indeed,  complex  members  of  the 
class,  and  especially  those  belonging  at  the  same  time 
to  two  or  more  classes,  often  do  not  give  them  at  all. 
Moreover,  many  of  the  reactions  are  general  for  more 
than  one  class;  but,  when  this  is  true,  it  will  be  pointed 
out,  as  far  as  practicable,  in  the  notes  following  the 
experiments. 

Statements  of  what  occurs  are  omitted  from  the 
following  directions  ;  and  the  student  is  expected  to 
observe  carefully  and  record  fully  in  the  note-book 
everything  that  happens,  even  those  things  of  appar- 
ently minor  importance.  Attention  should  be  directed 
not  only  to  what  may  be  seen,  but  also  to  any  odor  or 
to  any  heat  effect  developed.  The  observed  phenom- 
ena should  then  be  fully  explained  with  reference  to 
the  new  compounds  formed  ;  and  all  the  reactions 
where  known  products  are  formed  should  be  written, 


6  ORGANIC  LABORATORY  EXPERIMENTS, 

using  structural  formulae.  Works  on  organic  chemis- 
try should  be  consulted  when  necessary.  The  notes 
following  the  experiments  must  be  very  carefully 
studied. 

After  completing  the  experiments,  make  a  table  in 
the  note-book  showing,  as  far  as  possible,  the  behavior 
of  each  class  of  compounds  towards  each  of  the  follow- 
ing reagents :  cold  dilute  alkaline  hydroxides ;  boiling 
concentrated  alkaline  hydroxides  ;  concentrated  sulphu- 
ric acid  alone  and  with  subsequent  addition  of  water ; 
sodium  ;  and  bromine  water. 

Students  are  warned  that  many  of  the  reactions 
may  take  place  suddenly  and  with  great  violence, 
and  that,  therefore,  cautious  manipulation  is  neces- 
sary, particularly  in  test-tube  experiments. 

Behavior  of  Organic  Substances  on  Ignition. 

1.  Ignite  in  a  small  crucible,  as  long  as  any  change 
occurs,  first  a  little  benzoic  acid,  and  then  a  little  starch. 

Repeat  the  experiment  with  a  little  anhydrous  so- 
dium acetate.  Add  a  drop  of  dilute  hydrochloric  acid 
to  the  residue  after  cooling. 

This  reaction  with  hydrochloric  acid  is  given  only  by  organic 
salts  of  the  alkalies  and  alkaline  earths. 

Detection  of  Water  in  Organic  Liquids. 

2.  Add  0.2  gram  of  fused  pulverized  potassium  car- 
bonate to  5.  cc.  of  common  95  per  cent,  alcohol.     Shake 
and  set  aside  for  an  hour. 

Repeat  this  experiment,  using  5  cc.  of  the  same 
alcohol  diluted  with  1  cc.  of  water. 

3.  Add    0.5   gram   copper  sulphate,   freshly  dehy- 
drated by  ignition  at  a  low  temperature,  to  5  cc.  of 


CLASS  REACTION'S.  7 

ordinary  95  per  cent,  alcohol.      Shake  and  allow  the 
mixture  to  stand  for  about  one  hour. 


Reactions  Distinguishing  Double  and  Triple-Bonded 
from  Single-Bonded  Compounds. 

~~>y       f»      ^ 

4#.     Dissolve  0.5  gram  of  amylene  in  5  cc.  of  carbon      J^l/. 
-  ..tetrachloride,  and  add  gradually  a  10  per  cent,  solution     ] a^L- 
•     of  bromine  in  carbon  tetrachloride  as  long  as  any  action   . 

occurs.  J^ 

Repeat  this  experiment,  using  first  cinnamic  acid^^N^ 
then  phenol,  and  finally  toluene,  in  place  of  the  amy- 
lene.    In  the  cases  of  the  cinnamic  acid  and  toluene, 
after  allowing  the  mixture  to  stand  in  the  cold  for  two 
or  three  minutes,  heat  it  to  boiling  for  about  a  minute. 

Decolorization  without  evolution  of  hydrobromic  acid  shows 
addition,  and  therefore  the  probable  presence  of  a  double  or 
triple  bond.  Decolorization  accompanied  by  evolution  of  hydro- 
bromic acid  shows  substitution;  but  it  does  not  necessarily  ex- 
clude the  possibility  of  a  simultaneous  addition,  which  may  even 
be  inferred  in  case  the  evolution  of  hydrobromic  acid  is  not  pro- 
portionate to  the  rate  of  decolorization.  If  even  on  heating  no 
action  occurs,  or  if  only  a  slow  action  accompanied  by  evolution 
of  hydrobromic  acid  takes  place,  it  is  probable  that  no  double 
or  triple  bond  is.  present;  it  is  true,  nevertheless,  that  there  are 
some  double-bonded  compounds  (for  example,  fumaric,  maleic, 
and  the  nitro-cinnamic  acids)  which  form  addition-products  only 
very  slowly  or  not  at  all  under  the  conditions  of  this  experiment. 
On  the  other  hand,  amines,  phenols,  and  most  aldehydes  and  ke- 
tones,  like  double-bonded  compounds,  decolorize  the  ^bromine  so- 
lution instantly;  -in  the  case  of  amines,  often  without  evolution 
of  hydrobromic  acid. 

4£.  Dissolve  0.5  cc.  of  allyl  alcohol  in  5  cc.  of  water, 
and  gradually  add  bramine  water  as  long  as  decoloriza- 
tion takes  place. 


8  ORGANIC  LABORATORY  EXPERIMENTS. 

Repeat  the  experiment,  using  ethyl  alcohol  instead 
of  allyl  alcohol. 

As  bromine  water  is  used  as  a  reagent  in  other  cases,  this 
experiment  is  introduced  here,  in  order  to  show  its  behavior  with 
unsaturated  compounds.  But,  as  a  means  of  distinguishing  them 
from  saturated  bodies,  the  test  in  carbon  tetrachloride  is  far  more 
satisfactory:  for,  when  water  is  used  as  the  solvent,  any  hydro- 
bromic  acid  formed  is  absorbed  by  it,  so  that  it  is  not  readily 
possible  to  distinguish  substitution  from  addition;  moreover,  be- 
sides these  two  actions,  oxidation  often  takes  place  in  aqueous 
solution ;  and  finally,  the  unsaturated  compounds  which  fail  to 
react  in  carbon  tetrachloride  are  almost  equally  inert  in  water, 
so  that  the  latter  solvent  has  no  advantage  in  this  respect. 

5.  Add  0.2  gram  of  cinnamic  acid  to  5  cc.  of  so- 
dium carbonate  solution,  and  then  add   drop  by  drop 
about  1  cc.  of  a  one  per  cent,  solution  of  potassium 
permanganate. 

Repeat  the  experiment,  using  first  amylene  and 
then  toluene  in  place  of  the  cinnamic  acid. 

The  oxidation  takes  place  almost  instantaneously  with  unsatu- 
rated compounds,  and  with  some  saturated  ones,  such  as  formic 
acid,  malonic  ether,  phenols,  oxybenzoic  acids,  benzaldehyde,  ace- 
tone, acetophenone,  glycerine,  and  some  sugars.  But  most  satu- 
rated compounds  are  oxidized  much  more  slowly,  if  at  all. 

Reactions  of  Triple-Bonded  Compounds  Containing  the 
( =  C  —  H)  Group. 

6.  Add  1  cc.  of  ammoniacal  cuprous  chloride  solu- 
tion to  10  cc.  of  a  saturated  aqueous  solution  of  acety- 
lene and  shake. 

Behavior  Distinguishing  Saturated  Fatty  Compounds 
Containing  No  Complex  Alky  I  Radicals  from  Other 
Compounds. 

7.  Roll  a  piece  of  fine  copper  gauze  1  cm.  square 
around  the  end  of  a  copper  wire.     Dip  this  in  succes- 


CLASS  REACTION'S.  9 

sion  into  small  tubes  containing  (a)  toluene,  (b)  ben- 
zoic  acid,  (c)  allyl  alcohol,  (d)  sugar,  (e)  ethyl  ether, 
and  (/)  amyl  alcohol.  (In  the  case  of  the  solid  sub- 
stances, take  care  to  make  a  considerable  amount 
adhere  to  the  gauze.)  Hold  the  substance  in  a  gas 
flame  until  it  takes  fire ;  then  remove  it,  and  note 
whether  soot  is  produced,  holding  a  piece  of  white 
paper  behind  the  burning  substance. 

Almost  all  aromatic  compounds,  hydrocarbons,  unsaturated 
fatty  compounds,  and  fatty  compounds  containing  alkyl  radi- 
cals with  four  or  more  carbon  atoms,  when  they  can  be  burnt 
as  here  described,  produce  soot  in  considerable  quantity.  Other 
fatty  compounds  under  the  same  conditions  produce,  as  a  rule,  no 
soot. 

Behavior  of  Hydrocarbons  in  General. 

8.  Add  1   cc.   of  toluene  first  to  5  cc.  of  water, 
and  then  to  5  cc.  of  dilute  sodium  hydroxide  solution 
(1  :  10),  and  shake. 

Many  solid  aromatic  hydrocarbons  are  heavier  than  water. 

9.  Add  a  thin  slice  of  sodium  to  a  few  cubic  centi- 
meters of  toluene  in  a  perfectly  dry  test-tube. 

In  the  case  of  solid  substances  or  in  case  only  a 
slight  effervescence  occurs,  the  test  should  be  made 
as  illustrated  by  the  following  experiment. 

10.  Fill  a  small  test-tube  completely  with   anhy- 
drous alcohol-free  ether;   drop  to   the   bottom  a  thin 
slice  of  bright  sodium  (3  cm.  long,  1  cm.  wide) ;  and 
insert   at    once  a  clean,   dry  rubber   stopper,   through 
which  passes  a  small  glass  tube  which  reaches  nearly 
to  the   bottom    of   the   test-tube  and  is  there  turned 
upwards    for   a   distance    of    a    few    millimeters,    and 
which    is   bent    above  the   stopper   so    as    to    deliver 
into  another  test-tube.     Allow  the  action  to  continue 


10  ORGANIC  LABORATORY  EXPERIMENTS. 

for  fifteen  minutes,  and  make  a  mark  on  the  tube  to 
show  the  amount  of  gas  produced. 

Dissolve  1  gram  of  naphthalene  in  a  test-tube  full  of 
the  same  ether,  and  repeat  the  above  experiment. 

The  ether  for  this  experiment  will  be  found  in  the  laboratory. 
It  is  prepared  by  washing  commercial  ether  eight  or  ten  times 
"with  small  quantities  of  strong  salt  solution,  drying  it  for  at  least 
one  day  over  a  large  quantity  of  calcium  chloride,  treating  through 
several  days  with  successive  portions  of  sodium,  and  finally  distill- 
ing over  sodium  with  every  precaution  to  avoid  access  of  moisture. 
The  product  should  be  kfept  over  sodium  in  a  bottle  provided  with 
a  drying  tube. 

Reactions  Distinguishing  Hydrocarbons  of  the  MetJianc 
(CnH2n  +  2)  from    Those  of  the  Benzene  (CnH2n  _  6) 

Series. 

- 

11.  Thoroughly  mix  together  by  shaking  in  a  wide 
test-tube  2  cc.  of  petroleum  ether  and  5  to  6  cc.  of  w 
fuming  sulphuric  acid  (sp.  gr.  1.89  at  20°).     Pour  the 
mixture  very  slowly  and  cautiously  into  three  volumes 

of  cold  water,  and  allow  it  to  stand  a  few  minutes. 

Repeat  this  experiment,  using  toluene  instead  of 
petroleum  ether. 

12.  Repeat  both   parts  of   Experiment  11,   using 
fuming  nitric  acid  (sp.  gr.  1.48)  in  place  of  sulphuric 
acid.      As  the  action  may  suddenly  become  very  vio- 
lent, great  care  must  be  taken  to  hold  the  tube  in  such 
a  position  that  its  contents  cannot  be  thrown  out  upon 
the  experimenter. 

In  the  case  of  entirely  unknown  substances,  very  small  quan- 
tities should  first  be  experimented  with. 


CLASS  REACTIONS.  11 

Behavior  of  Halogen-Substituted  Hydrocarbons. 

13.  Add  1  cc.  of  ethyl  bromide  first  to  5  cc.  of 
water,"  and  then  to  5  cc.  of  dilute   sodium   hydroxide 
solution,  and  shake. 

The  monochlorinated  derivatives  of  the  fatty  hydrocarbons 
are  lighter  than  water. 

X       Reactions  Distinguishing  Halogen  Compounds  of 
Differ  en  t   Types . 

14.  Add   three   drops  of   ethyl   bromide  to  5  cc. 
of  an  alcoholic  solution   of  potassium   hydroxide  (free 
from  chlorine),  and  boil  gently  for  two  minutes.     Di- 
lute with  water,  acidify  with  nitric  acid,  and  add  a  few 
drops  of  silver  nitrate  solution. 

Repeat  this  experiment,  using  first  benzyl  chloride, 
and  then  brombenzene  in  place  of  the  ethyl  bromide. 

In  experimenting  with  unknown  substances,  in  order  to  make 
sure  that  they  contain  no  free  halogen  or  halogen  acid,  it  is  advis- 
able to  wash  them  with  dilute  sodium  carbonate  solution  before 
applying  the  test. 

The  behavior  of  ethyl  bromide  is  typical  of  halogen  com- 
pounds of  the  fatty  series;  that  of  benzyl  chloride,  of  aromatic 
compounds  containing  halogen  in  the  side  chain;  and  that  of 
brombenzene,  of  aromatic  compounds  having  halogen  attached 
to  an  aromatic  nucleus.  Some  halogen  compounds  of  the  lat- 
ter class,  especially  those  containing  also  a  nitro  group,  are  de- 
composed by  potassium  hydroxide  and  give  the  reaction  with 
silver  nitrate. 

Reaction  Distinguishing  Saturated  and  Aromatic  Hy- 
drocarbons and  Their  Halogen  Derivatives  from 
Other  Compounds. 

15.  Add  gradually,  shaking  constantly  and  keep- 
ing the  mixture  cool,  4  cc.  of  concentrated  sulphuric 


12  ORGANIC  LABORATORY  EXPERIMENTS. 

acid    to    2   cc.    of   (a)    toluene,   (b)    ethyl   bromide,    (c) 
phenol,  and  (d)  ethyl  acetate. 

The  behavior  with  cold  sulphuric^acid  will  generally  distin- 
guish saturated  and  aromatic  hydrocarbons  and  their  halogen 
derivatives  from  other  compounds,  most  of  which  are  either 
soluble  in  the  acid  or  are  destroyed  by  it.  Among  these  other 
compounds  there  are,  however,  many  which  are  unacted  upon  by 
sulphuric  acid,  but  these  exceptions  are  met  with  mostly  among 
the  acids  and  nitrogen  compounds.  The  test  is  therefore  espe- 
cially useful  in  distinguishing  hydrocarbons  and  their  halogen 
derivatives  from  alcohols,  phenols,  ethers,  and  esters. 

Reactions  of  Compounds  Containing  the  Hydroxyl 
Group. 

16.  Add  small  pieces  of  sodium  to  3  cc.  of  abso- 
lute  alcohol,   in  a  test-tube,   as   long   as   it   dissolves. 
The   sodium    should    be   added   fast    enough   to   keep 
the  solution  hot  without  causing  it   to  boil  violently. 
Finally,  cool  the  solution. 

Substances  to  which  this  test  is  to  be  applied  must  first  be 
thoroughly  dried,  if  water  is  present.  Solid  or  viscous  sub- 
stances must  be  dissolved  in  anhydrous  ether  or  some  other 
indifferent  solvent.  If  the  effervescence  is  only  slight,  the 
test  must  be  tried  as  described  in  Experiment  10,  in  order  to 
form  an  idea  of  the  amount  of  gas  evolved,  and  thus  distin- 
guish a  slow  action  on  a  hydroxyl  compound  from  that  due  to 
an  impurity. 

Besides  hydroxyl  compounds,  some  aldehydes,  ketones,  esters, 
and  amides  evolve  hydrogen  ;  and  the  halogen  compounds  of  the 
lower  hydrocarbons  of  the  ,fatty  series  give  off  gaseous  hydro- 
carbons. On  the  other  hand,  a  few  hydroxyl  compounds  (for 
example,  resorcin,  and  salicylic  acid)  fail  to  give  evidence  of  a 
reaction  with  sodium. 

Reactions  of  Alcohols  and  Phenols. 

17.  Add  gradually  2  cc.  of  amyl  alcohol  to  4  cc.  of 
concentrated  sulphuric  acid  in  a  small  test-tube,  shak- 


CLASS  REACTIONS.  13 

ing  constantly  and  keeping  the  mixture  cool.  Allow 
it  to  stand  two  or  three  minutes,  and  then  pour  it 
into  a  test-tube  containing  about  12  cc.  of  water. 

Repeat  the  experiment,  using  phenol  in  place  of 
the  amyl  alcohol. 

In  the  case  of  the  higher  fatty  alcohols  a  layer  consisting  of  the 
original  alcohol  or  some  insoluble  reaction-product  may  separate 
out  on  the  dilution  of  the  sulphuric  acid.  Compare  Experiment  32. 

If  the  substance  to  be  tested  is  soluble  in  water,  it  is  not 
possible  to  determine  in  this  simple  manner  whether  or  not  it 
combines  with  the  sulphuric  acid.  In  that  case  the  method 
illustrated  by  the  following  experiment  must  be  employed. 

18.  Mix  2  cc.  of  strong  sulphuric  acid  with  5  cc. 
of  alcohol.     After  five  minutes  pour  the  mixture  into 
100  cc.  of  water,  heat  to  boiling,  and  add  barium  car- 
bonate until  the  liquid  is  neutral.      Filter  hot.      Add 
dilute  sulphuric  acid  to  one-half  of  the  filtrate.     Evap- 
orate the  other  half  to  dryness  and  ignite  the  residue. 

Of  the  alcohols,  only  the  primary  ones  of  the  fatty  series 
give  the  reactions  observed  in  this  experiment  Phenols  and 
some  other  aromatic  compounds,  however,  give  apparently  the 
same  result,  owing  to  the  formation  of  soluble  sulphonic  acids 
and  soluble  barium  sulphonates 

19.  Add  2  cc.  of  acetyl  chloride  to   (a)  1   cc.  of 
ethyl  alcohol  and  (b)  1  gram  of  phenol,  and  add  the 
mixtures   to  5  cc.  of   water.      Use   great   caution,  as 
the  reactions  with  acetyl  chloride  are  sometimes  very 
violent. 

Reactions  of  Alcohols. 

20.  Test  the  solubility  of  ethyl  alcohol  and  of  amyl 
alcohol  in  water  and  dilute  sodium  hydroxide  solutions. 

All  monoatomic  alcohols  containing  less  that  four  atoms  of 
carbon  and  almost  all  polyatomic  alcohols  are  readily  soluble 
in  water;  other  alcohols  are  insoluble  or  difficultly  soluble. 


14  ORGANIC  LABORATORY  EXPERIMENTS. 

21.  Place  in  a  small  flask  2  cc.  of  alcohol,  50  cc. 
of  sodium  hydroxide  solution  (1  :  10)  and  5  cc.  of  ben- 
zoyl  chloride.      Shake  until  the  odor  of  benzoyl  chlo- 
ride has  disappeared. 

Repeat  the  experiment,  omitting  the  alcohol. 

The  odor  observed  in  this  experiment  is  a  characteristic  and 
delicate  test  for  the  lower  monoatomic  alcohols  of  the  fatty  series. 
Hydroxyl  compounds  in  general,  with  the  exception  of  acids,  un- 
dergo a  similar  reaction  ;  but  the  products  do  not  possess  the  same 
characteristic  odor. 

Reactions  of  Phenols. 

22.  Test  the  solubility  of  phenol  in  water,  in  so- 
dium carbonate  solution,  and  in  sodium  hydroxide  solu- 
tion by  adding  the  solvents  little  by  little  to  1-2  grams 
of  the  substance.      Test  the  solubility  of  resorcin  in 
water.     Test  the  reaction  of  the  aqueous  solutions  with 
alkaline  phenolphthalein   solution  or  with  blue  litmus 
paper. 

23.  Add  a  few  drops  of  ferric  chloride  solution  to 
solutions  of  phenol,  of  pyrocatechin,  and  of  resorcin. 

.This  test  is  applicable  to  neutral  solutions  only.  In  order 
that  it  may  be  regarded  as  indicating  the  presence  of  a  phenol, 
a  strong  coloration  must  be  obtained;  for  most  hydroxyl  deriva- 
tives give  a  faint  yellow  coloration.  The  most  important  phenols 
that  fail  to  give  this  reaction  are  a-naphthol,  the  nitrophenols, 
and  meta  and  para  oxyacids.  On  the  other  hand,  many  aromatic 
amines  give  similar  colorations;  and  oxyacids  of  the  fatty  series 
give  a  strong  yellow  coloration  (compare  Experiment  30). 

24.  Heat   together  in   dry  test-tubes   for   one   or 
two  minutes  in  an  oil-bath  at  a  temperature  of  150°,  0.2 
gram  phthalic  anhydride  and  a  somewhat  smaller  quan- 
tity of  phenol,  a-naphthol,  resorcin,  and  pyrocatechin, 
the  mixtures  being  first  moistened  (not  covered)  with  a 


CLASS  REACTIONS.  15 

few  drops  of  concentrated  sulphuric  acid.  Treat  the 
fused  mass  with  10  cc.  of  cold  water,  and  add  so- 
dium hydroxide  solution  very  gradually  until  no  fur- 
ther change  occurs.  Dilute  portions  of  the  faintly 
alkaline  solutions,  and  view  them  obliquely  from 
above  by  reflected  light. 

25.  Add  bromine  water  to  5  cc.  of  phenol  solution 
until  the  liquid  assumes  a  permanent  yellow  color. 

This  reaction  is  a  very  delicate  one  for  most  phenols,  but 
there  are  a  few  exceptions.  Moreover,  many  aromatic  amines 
also  give  a  precipitate  with  bromine  water. 

Reactions  of  Organic  Acids. 

26.  Test  the  solubility  in  water  of  benzoic  acid  and 
oxalic  acid. 

Nearly  all  acids  containing  more  than  six  carbon  atoms,  ex- 
cept the  aromatic  sulphonic  acids,  are  insoluble  or  very  difficultly 
soluble  in  cold  water.  On  the  other  hand,  nearly  all  of  the  acids 
commonly  met  with  containing  a  smaller  number  of  carbon  atoms 
are  soluble. 

27.  To  about  0.2  gram  of  benzoic  acid  add,  in  por- 
tions of  1  cc.  at  a  time,  a  one  per  cent,  solution  of  so- 
dium hydroxide  strongly  colored  by  the  addition  of  a 
little  phenolphthalein  solution. 

In  order  to  distinguish  between  considerable  amounts  and 
accidental  traces  of  acids,  the  test  is  made  in  this  way,  so  as 
to  determine  roughly  the  quantity  of  alkali  required  for  the 
neutralization. 

Some  esters  are  so  readily  saponified  that  they  cause,  when 
tested  as  here  described,  a  rapid  decolorization  of  the  solutions ; 
but  the  action  is  never  instantaneous,  as  is  the  case  with  most 
acids. 

28.  Treat   1  gram  of  benzoic  acid  with  5  cc.  of 
water;  add  sodium  carbonate  solution,  at  first  in  small 


16  ORGANIC  LABORATORY  EXPERIMENTS. 

quantity,  and  finally  in  slight  excess  ;  then  acidify  with 
^hydrochloric  acid. 

29.  Add  20  cc.  of  sodium  formate  solution  (1  :  5) 
to  0.5  gram  (weighed  approximately)  of  the  following 
acids  in  the  state  of  fine  powder :  Benzoic,   salicylic, 
phthalic,  cinnamic. 

All  these  acids  are  nearly  insoluble  in  water.  The  experi- 
ment determines  roughly  the  strength  of  the  various  acids  as 
compared  with  formic  acid.  Those  stronger  than  formic  acid 
displace  it  and  go  into  solution ;  those  weaker  do  not.  The 
strength  of  acids  depends  on  their  composition  and  structure. 
Of  the  aromatic  acids,  the  sulphonic  acids  and  the  derivatives  of 
benzoic  acid  and  its  homologues  containing  one  or  more  nitro 
groups,  or  two  or  more  halogens,  or  one  halogen,  hydroxyl  or 
carboxyl  group  in  the  ortho  position  to  the  carboxyl  group,  are 
stronger  than  formic  acid.  Acids  containing  none  of  the  men- 
tioned "negative  "  groups,  or  containing  one  halogen  in  the  meta 
or  para  position,  or  one  or  more  hydroxyl  groups  in  the  meta  or 
para  position,  are  weaker  than  formic  acid.  (For  a  detailed  list 
of  the  strengths  or  "affinity  constants  "  of  various  acids  see  the 
Zeitschrift  fiir  physikalische  Chemie,  3,  418.) 

Reaction  of  a-Oxy-acids. 

30.  Dissolve  0.1  gram  of  tartaric  acid  in  50  cc.  of 
cold  water,  in  a  porcelain  dish,  and  add  two  drops  of 
a  10  per  cent,  ferric  chloride  solution. 

Repeat  the  experiment,  using  sugar  in  place  of  tar- 
taric  acid. 

As  is  illustrated  by  the  latter  part  of  this  experiment,  hy- 
droxyl compounds  in  general  give  a  slight  coloration ;  but  the 
color  produced  by  the  a-oxy-acids  is  very  much  stronger  at  the 
same  concentration.  It  is,  moreover,  always  a  pure  yellow. 

Reactions  of  Ethers  and  Esters. 

31.  Add  1  cc.  of  ethyl  ether  first  to  5  cc.  of  water, 
and  then  to  5  cc.  of  dilute  sodium  hydroxide  solution. 


CLASS  REACTIONS.  17 

Repeat  the  experiment,  using  amyl  acetate  in  place 
of  ethyl  ether. 

32.  Repeat  Experiment  17,  using  first  ethyl  ether 
and  then  amyl  acetate  in  place  of  amyl  alcohol. 

Reactions  of  Compound  Ethers  or  Esters. 

33.  Boil  vigorously  over  a  small  free  flame  3  cc.  of 
ethyl  benzoate  with  80  cc.  of  potassium  hydroxide  solu- 
tion (1  :  4)  in  a  200  cc.  long-necked,  round-bottomed 
(Kjeldahl)  flask  provided  with  a  long  return  cooler  of 
wide  bore,  until  the  odor  of  the  ester  disappears.     Acid- 
ify half  the  solution  with  an  excess  of  hydrochloric  acid. 
Dilute  the  remainder  with  water  to  100  cc.,  add  5  cc. 
of  benzoyl  chloride,  and  shake  till  its  odor  has  disap- 
peared, as  in  Experiment  21. 

Since  the  ease  of  saponification  varies  greatly  with  the  nature 
of  the  ester,  the  boiling  should  be  continued  until  complete  solu- 
tion takes  place,  or  until  the  ethereal  odpr  disappears. 

If  the  alcohol  of  the  ester  is  insoluble,  and  if  the  acid  of  it 
is  soluble  in  water,  evidently  the  ester  would  not  be  detected  by 
the  method  illustrated  by  the  above  experiment  (except,  perhaps, 
by  the  disappearance  of  its  odor).  In  case,  therefore,  the  above 
test  gives  a  negative  or  indecisive  result,  proceed  as  in  the  fol- 
lowing experiment. 

34.  Introduce  into  a  long-necked,  round-bottomed 
flask  of  200  cc.  capacity  50  cc.  of  a  6  per  cent,  alcoholic 
potassium  hydroxide  solution  measured  accurately  by 
means  of  a  pipette.     Add  to  it  3  c«.  of  ethyl  acetate. 
Connect  the  flask  in  an  inclined  position  with  a  return 
cooler,  and  boil  vigorously  for  twenty  minutes.     Rinse 
off  the  condenser  and  stopper  into  the  flask,  dilute  to 
about  100  cc.,  add  a  drop  or  two  of  phenolphthalein 


18  ORGANIC  LABORATORY  EXPERIMENTS. 

solution,  and  titrate  with  hydrochloric  acid  (one  part  acid 
of  1.12  sp.  gr.  to  two  parts  of  water)  added  by  means  of 
a  graduated  pipette.  Titrate  in  the  same  way  50  cc. 
of  the  original  alcoholic  potassium  hydroxide  solution. 

In  case  of  unknown  substances,  if  an  appreciable  amount  of 
acid  is  found  to  be  present  by  the  test  described  in  Experiment 
27,  it  must  first  be  removed  by  washing  the  substance  with  so- 
dium carbonate  solution,  and  then  with  water. 

Aromatic  aldehydes  are  also  converted  by  potassium  hydrox- 
ide into  alcohols  and  acids.  Moreover,  amides,  nitriles,  some 
carbohydrates,  and  a  few  ketones  are  decomposed  with  formation 
of  acids  which  combine  with  the  potash. 

Reactions  of  Acid  Chlorides. 

35.  Add  a  few  drops  of  water  to  1  cc.  of  acetyl 
chloride. 

It  is  generally  necessary  to  heat  acid  chlorides  in  order  to 
produce  this  decomposition. 

Reactions  Common  to  Aldehydes  and  Ketones. 

36.  Test  the  solubility  of  benzaldehyde  in  water 
and  in  dilute  sodium  hydroxide  solution. 

The  lower  aldehydes  and  ketones  of  the  fatty  series  are, 
however,  readily  soluble  in  all  these  solvents.  Acetaldehyde  is 
converted  by  alkalies,  especially  on  heating,  into  aldehyde-resin, 
a  brown  amorphous  substance.  In  regard  to  aromatic  aldehydes, 
see  the  note  to  Experiment  34. 

Cold  concentrated  sulphuric  acid  either  dissolves  or  destroys 
aldehydes  and  ketones. 

37.  Shake  together  for  two  or  three  minutes  3  cc. 
of  acetone  and  5  cc.  of  a  saturated  solution  of  sodium 
acid  sulphite.     If  necessary,  set  aside  and  cool. 

This  reaction,  while  very  characteristic,  is  not  particularly 
delicate.  Ketones  give  it  only  when  they  contain  the  group 
-CH3.CO.  Solid  substances  should  be  dissolved  in  a  very  little 


CLASS  REACTIONS.  19 

ether.      In  applying  the  reaction  to  unknown  substances,  always 
test  the  reagent  first  with  a  portion  of  acetone. 

38.  To  5   cc.   of  aldehyde  solution  add  an   equal 
volume  of  sodium  acetate  solution  and  a  few  drops  of 
a  solution  of  phenylhydrazine  hydrochloride. 

This  test  is,  as  a  rule,  most  satisfactorily  applied  in  aqueous 
solution,  most  aldehydes  and  ketones  being  sufficiently  soluble 
in  water  for  the  purpose.  In  some  cases,  however,  it  is  neces- 
sary to  use  some  other  solvent  than  water;  but  in  that  case  a 
negative  result  is  not  decisive,  since  the  hydrazone  formed  may 
be  soluble. 

Reactions  of  Aldehydes  (not  Ketones}. 

39.  Mix  in  a  test-tube  previously  cleaned  with  hot 
sodium  hydroxide  solution  1  cc.  of  ammoniacal  silver 
nitrate  solution  and  1  cc.  of  ten  per  cent,  sodium  hy- 
droxide solution.     Shake  the  mixture  about  in  the  tube, 
and  then  allow  two  or  three  drops  of  aldehyde  solution 
to  flow  slowly  down  the  moistened  glass  surface.     Do 
not  warm  the  mixture. 

This  test  is  known  as  the  Tollen's  reaction  for  aldehydes. 
The  ammoniacal  silver  solution  contains  one  part  of  silver  nitrate 
dissolved  in  ten  parts  of  ammonia  water  of  sp.  gr.  0.923.  When 
mixed  with  sodium  hydroxide,  a  dangerously  explosive  precipi- 
tate is  apt  to  form  on  heating  or  on  long  standing. 

Some  compounds  other  than  aldehydes,  especially  di-atomic 
and  tri-atomic  phenols  and  amidophenols,  reduce  ammoniacal  sil- 
ver solution. 

40.  Pour  two  or  three  drops  of  aldehyde  solution 
into  5  cc.  of  cold  fuchsine-aldehyde-reagent. 

This  aldehyde-reagent  is  prepared  by  dissolving  one  part  of 
a  rosaniline  salt  in  one  thousand  parts  of  water,  and  then  adding 
enough  of  a  strong  sulphurous  acid  solution  to  destroy  the  red 
color  on  standing.  An  excess  of  sulphurous  acid  does  not  inter- 
fere with  the  reaction.  Some  ketones  when  added  to  the  reagent 
in  relatively  large  quantity  give  the  same  reaction  as  aldehydes  ; 
but  the  change  occurs  much  more  slowly. 


20  ORGANIC  LABORATORY  EXPERIMENTS. 

Reaction  for  Carbohydrates. 

41.  Add  to  pieces  of  sugar,  starch,  and  filter  paper 
not  larger  than  a  mustard  seed  0.5  cc.  of  water,  two 
drops  of  a   20  per  cent,  alcoholic   solution  of  a-naph- 
thol,  and  2  cc.  of  concentrated  sulphuric  acid.     Dilute 
with  water  and  add  a  slight  excess  of  potassium   hy- 
droxide solution. 

The  composition  of  the  compound  formed  is  unknown. 
The  tests  for  aldehydes  and  ketones  described  in  the  pre- 
ceding experiments  are,  as  a  rule,  not  applicable  to  carbohydrates. 

Reactions  of  Aromatic  Nitro-Compounds. 

42.  Add  1  cc.  of  nitrobenzene  to  5  cc.  of  water, 
to  5   cc.  of  dilute   hydrochloric   acid,  and   to  5   cc.  of 
dilute  sodium   hydroxide  solution. 

Nitro-compounds,  particularly  those  containing  two  or  more 
nitro  groups,  color  sodium  hydroxide  solution  deep  red  or  yellow. 

43.  Repeat  Experiment  17,  using  nitrobenzene  in 
place  of  the  amyl  alcohol. 

•  Trinitro-compounds  and  many  other  nitro-compounds  contain- 
ing other  substituted  groups  require  heat  for  their  solution  in 
sulphuric  acid. 

44.  To  1  cc.  of  nitrobenzene,  in  a  wide  test-tube, 
add  2—3  grams  of  granulated  tin  ;  and  then  add,  in  sev- 
eral small  portions,  5  cc.  of  hydrochloric  acid  of  1.2 
sp.  gr.,  with  constant  shaking.     The  temperature  and 
the  addition  of  the  acid  should  be  regulated  so  as  to 
secure  a  moderate  reaction.     In  order  to  complete  it, 
gentle  heat  and  the  addition  of  more  tin  or  acid  may 
be  necessary.      Pour  the  clear  solution  into  a  beaker, 
dilute  with  10  cc.  of  water,  and  add  potassium  hydrox- 
ide solution  (1 :  2),  until  the  solid  precipitate  formed  at 
first  has  for  the  most  part  redissolved. 


CLASS  REACTIONS.  21 

44A.  Dissolve  three  drops  of  .nitrobenzene  in  3  cc.  of 
50  per  cent,  alcohol.  To  this  solution  add  five  or  six 
drops  of  calcium  chloride  solution  (1  :  10)  and  a  pinch 
of  zinc  dust.  Heat  until  the  mixture  begins  to  boil 
briskly,  and  then,  after  allowing  it  to  stand  from  two 
to  five  minutes,  filter.  Add  the  filtrate  to  a  strongly 
ammoniacal  silver  nitrate  solution. 

-Nitroso,  azo,  and  azoxy  compounds  also  give  this  reaction.  It 
is,  of  course,  useless  to  apply  it  to  compounds  that  reduce  silver 
nitrate  before  treatment  with  zinc  dust. 

The  compound  formed  in  the  above  experiment  by  the  action 
of  the  zinc  dust  on  nitrobenzene  is  phenyl  hydroxylamine. 

The  effect  of  the  calcium  chloride  is  to  accelerate  the  reduction. 

44e.  Dissolve  three  drops  of  nitrobenzene  in  3  cc.  of 
a  light-colored  mixture  of  equal  parts  of  aniline,  <?-tolu- 
idine  and  /-toluidine.  Add  2  cc.  of  water,  2  cc.  of 
hydrochloric  acid  (sp.  gr.  1.20),  and  about  1  gram  of 
iron  filings.  The  liquid  reagent  should  be  measured 
out  carefully  from  a  small  graduate.  Boil  the  mixture 
from  one  to  three  minutes,  and  then  pour  off  a  little 
of  the  dark-colored  solution  into  a  test  tube  half  filled 
with  dilute  acetic  acid. 

This  test  depends  on  the  formation  of  rosaniline,  and  is  given 
not  only  by  nitro-compounds,  but  by  all  other  organic  compounds 
in  which  oxygen  is  directly  united  to  nitrogen  and  by  some  inor- 
ganic oxidizing  agents.  Very  volatile  nitro-compounds  and  such 
as  contain  several  nitro  groups  may  fail  to  show  it. 


22  ORGANIC  LABORATORY  EXPERIMENTS. 

Reactions  of  Amines. 

45.  Test   the    solubility   of   aniline   in    water   and 
dilute  hydrochloric  acid  (1  :  10) ;    and  then  make  the 
acid  solution  alkaline  with  potassium  hydroxide. 

Aromatic  amines  containing  negative  substituted  groups  (for 
example,  dinitraniline)  or  two  or  more  aromatic  radicals  (for  exam- 
ple, triphenylamine)  often  may  not  dissolve  in  hydrochloric  acid 
of  this  strength,  owing  to  the  decomposition  of  their  salts  by 
water. 

46.  Dissolve  a  little  aniline  in  the  least  possible 
amount  of  hydrochloric  acid,  and  add  a  few  drops  of 
this  solution  to  1  cc.  of  hydrochloroplatinic  acid. 

The  platinum  salts  of  many  amines  are  soluble,  and  there- 
fore do  not  precipitate  under  these  conditions. 

47.  Add  acetyl  chloride  cautiously,  drop  by  drop, 
to  1  cc.  of  aniline,  in  a  small  flask,  until  there  is  no 
longer  any  apparent  action.      Add  carefully  25  cc.  of 
water  to  the  product. 

Tertiary  amines  and  most  amines  containing  negative  groups 
fail  to  react  with  acetyl  chloride  in  the  cold. 
Compare  Experiment  19. 

48.  Add  gradually  an  excess  of  bromine  water  to 
a  drop  of  aniline  suspended  in  2  cc.  of  water. 

Compare  Experiment  25. 

Reactions  Distinguishing  Amines   of  Different   Types. 

49.  Warm  under  a  hood  one  or  two  drops  of  ani- 
line, to  which  a  few  drops  of  chloroform   have  been 
added,  with  1  or  2  cc.  of  alcoholic  potassium  hydroxide 
solution. 

Only  primary  amines  give  rise  to  the  odor  observed  in  this 
experiment.  The  test  is  so  delicate,  however,  that  it  is  difficult 


23 

to  distinguish  by  means  of  it  a  minute  trace  of  a  primary  amine 
from  a  considerable  amount.  The  following  experiment  enables 
us  to  do  this  with  certainty. 

50.  Add  to  1  gram  of  aniline  in  a  test-tube  5  cc. 
of  water  and  5  cc.  of  hydrochloric  acid  (sp.  gr.  1.12). 
Cool  the  solution   in   ice  water,  and  add  to  it  gradu- 
ally, keeping  it  well  cooled,  about   3  cc.  of  a  sodium 
nitrite  solution  (1  :  3),  until,  after  shaking,  the  mixture 
smells  distinctly  of   nitrous   acid.      Now  insert  in  the 
test-tube  a  stopper  with  a  delivery  tube,  and  warm  the 
mixture  gently,   collecting  the  gas  evolved   in  an   in- 
verted 200  cc.    bottle   filled  with  a  saturated  ferrous 
sulphate  solution  ;   shake    the  bottle  until  no  further 
absorption  of  gas  takes  place. 

Repeat  the  experiment,  using  first  methylaniline, 
and  then  dimethylaniline,  in  place  of  aniline. 

Amides  are  also  decomposed  with  evolution  of  gas,  but  as 
a  rule  less  readily  than  amines.  The  reaction  is,  indeed,  al- 
most universally  applicable  for  the  detection  of  the  NH2  group 
in  amines  appreciably  soluble  in  dilute  hydrochloric  acid,  even 
substitution-products  like  sulphanilic  acid,  undergoing  the  reac- 
tion readily. 

51.  Add  very  cautiously  1   cc.  of  acetyl  chloride 
first  to  1  cc.  of  methylaniline,  and  then  to  1  cc.  of 
dimethylaniline. 

Compare  the  results  with  those  of  Experiment  47. 

52.  Add  to  about   0.5  gram   of  aniline  50   cc.  of 
potassium  hydroxide  (1  :  4)  and  2  grams  of  benzenesul- 
phonyl  chloride,  shake  for  two  or  three  minutes,  and 
then   warm   till    the   odor   of   the   chloride   disappears. 
Acidify  the  solution  with  hydrochloric  acid. 

Repeat  the  experiment,  using  first  methylaniline, 
and  then  dimethylaniline,  in  place  of  the  aniline.  In 


24  OR  GA  NIC  LAB  OR  A  TO  R  Y  EX  PER  I.  ME  NTS. 

these  two  cases  filter  before  acidifying  the  solution, 
and  test  the  solubility  of  the  precipitate  on  the  filter 
in  dilute  hydrochloric  acid. 

Reactions  of  Amides  and  Nitrites. 

53.  Test  the  solubility  of  urea  and  of  acetanilide 
in  water,   and  that  of   the  latter  substance   in  dilute 
hydrochloric  acid  (1  :  10). 

54.  Boil  1  gram  of  urea  with  5  cc.  of  potassium 
hydroxide  solution  for  two  or  three  minutes.     Acidify 
the  solution  with  sulphuric  acid. 

Repeat  the  experiment,  using  acetanilide  in  the 
place  of  urea. 

Ammonium  salts  and  those  of  amines  are  readily  decomposed 
by  potassium  hydroxide  in  the  cold.  Some  amides  (for  example, 
urea)  are  also  slowly  decomposed  in  the  cold,  but  there  is  little 
danger  of  confounding  them  with  ammonium  salts. 

Nitriles,  like  amides,  are  decomposed  by  boiling  with  alkalies; 
but  the  former  may  usually  be  distinguished  from  the  latter  by 
their  greater  volatility. 

Reaction  of  Aromatic  Sulphonic  Acids. 

55.  Fuse  1  gram  of  sodium  hydroxide  in  a  small 
nickel  or  porcelain  crucible  heated  on  an   iron  plate. 
Add  to  the  fused  mass  about  0.5  gram  of  sodium  ben- 
zenesulphonate ;   and   continue   the   heating  for  about 
five  minutes,  with  occasional  stirring,   regulating  the 
temperature  so  that  the  mass  remains  liquid,  and  so 
that  it  does  not  char.     After  cooling,  dissolve  the  prod- 
uct in  water,  acidify  with  dilute  hydrochloric  acid,  fil- 
ter, and  add  bromine  water. 


SPECIAL   REACTIONS.  25 

Special  Reactions  of  Methyl  Alcohol  and  Ethyl  Alcohol. 

56.  Wind  a  piece  of  copper  wire  around  a  lead 
pencil  so  as  to  form  a  close  spiral  about  1.5  cm.  long, 
leaving  about   20  cm.  of  straight  wire  to  serve  as  a 
handle.      Heat  the  spiral  to  redness  in  the  oxidizing 
flame  of  a  Bunsen  burner,   and  plunge   it   while  still 
glowing  into  3  cc.  of  water,  to  which  a  few  drops  of 
methyl  alcohol  have  been  added.      Remove  the  spiral 
immediately,  cool  the  solution,  and  add  to  it  one  drop 
of  a  half  per  cent,  aqueous  resorcine  solution.      Pour 
the  mixture  cautiously  down  the  side  of  an   inclined 
test-tube   containing  5  cc.   of   concentrated    sulphuric 
acid   so  that  it  may  form   a  distinct  layer  above  the 
acid.     After  observing  the  immediate  result  following 
the  contact  of  the  two  liquids,  set  the  tube  aside  for 
a  few  hours. 

Repeat  this  experiment,  using  in  place  of  the 
methyl  alcohol  first  ethyl  alcohol,  and  then  a  mixture 
of  one  volume  of  methyl  alcohol  with  five  volumes  of 
ethyl  alcohol. 

Unknown  substances  containing  difficultly  volatile  constitu- 
ents should  be  first  distilled,  after  neutralizing  with  sodium  car- 
bonate if  acid,  and  the  above  test  should  then  be  applied  to  an 
aqueous  solution  of  the  distillate  passing  over  below  100°,  as 
many  difficultly-volatile  substances  give  reactions  that  would  ob- 
scure the  color. 

Methyl  esters  and  ethers  also  generally  give  this  reaction, 
owing  to  partial  decomposition  into  methyl  alcohol. 

The  colored  compound  formed  in  the  experiment  is  a  compli- 
cated condensation-product  of  resorcine. 

57.  To  5  cc.  of  a  5  per  cent,  ethyl  alcohol  solution 
add  two  or  three  drops  of  sodium  hydroxide  solution 
(1  :  10),  warm  to  about  50°,  and  drop  in,  with  con- 


26  ORGANIC  LABORATORY  EXPERIMENTS. 

stant  shaking,  a  concentrated  solution  of  iodine  in 
potassium  iodide,  until  the  liquid  becomes  perma- 
nently brown.  Finally  carefully  decolorize  by  a  fur- 
ther addition  of  sodium  hydroxide.  Allow  the  mixture 
to  stand. 

Repeat  the  experiment,  but  without  warming,  using 
an  aqueous  solution  of  acetone. 

As  in  the  case  of  the  methyl  alcohol  reaction,  this  test,  when 
applied  to  unknown  substances,  should  be  tried  with  an  aqueous 
solution  of  the  distillate  boiling  below  100°. 

Some  other  volatile  substances  besides  ethyl  alcohol  and 
acetone  show  this  reaction,  among  which  may  be  specially 
mentioned  acetaldehyde  and  isopropyl  alcohol. 


ELEMENTARY  COMPOSITION.  27 


PART    II. 

EXPERIMENTS  ILLUSTRATING  THE  METHODS  OF  DETEC- 
TION OF  NITROGEN,  SULPHUR,  AND  HALOGENS  IN 
ORGANIC  COMPOUNDS. 

Subject  portions  of  aniline,  sulphurea,  chloroform, 
and  bromnitrobenzene,  each  separately,  to  the  follow- 
ing treatment : 

Preparation  of  the  Solution.  —  Prepare  an  ignition- 
tube  about  four  inches  in  length  from  a  piece  of  hard 
glass  combustion-tubing.  Warm  the  closed  end  by 
passing  it  rapidly  back  and  forth  through  a  flame. 
Then  support  the  tube  in  a  vertical  position  by  a 
clamp,  and  drop  in  a  piece  of  pure  sodium  as  large 
as  a  pea.  Place  a  small  flame  directly  beneath  the 
ignition-tube,  and  quickly  heat  the  bottom  of  it  to 
redness.  As  soon  as  the  vapor  of  the  melted  so- 
dium forms  a  layer  half  an  inch  in  height,  allow 
about  five  drops  of  the  substance  if  a  liquid,  or  an 
equivalent  quantity  of  fragments  if  a  solid,  to  fall  at 
intervals  of  one  or  two  seconds  directly  upon  the  red- 
hot  bottom  of  the  tube  without  touching  its  side  walls. 
When  the  tube  has  become  cold  remove  any  excess  of 
metallic  sodium  by  adding  a  very  little  alcohol.  Next, 
add  very  cautiously  a  little  distilled  water,  stir  well 
with  a  glass  rod,  rinse  the  contents  of  the  ignition-tube 
into  a  test-tube,  bring  to  a  boil,  and  filter.  The  filtrate 
should  be  nearly  colorless  and  measure  about  15  cc. 
Separate  portions  of  this  filtrate  are  to  be  used  in  the 
following  tests : 


28  ORGANIC  LABORATORY  EXPERIMENTS. 

Tests  for  Sulphur.  —  To  1  cc.  of  the  prepared  so- 
lution add  two  or  three  drops  of  a  dilute  sodium  nitro- 
prusside  solution. 

To  1  cc.  add  two  or  three  drops  of  a  solution  of  lead 
acetate  made  strongly  alkaline  with  sodium  hydroxide. 

Only  alkaline  sulphide  solutions  give  the  reaction  with  so- 
dium nitroprusside. 

Test  for  Nitrogen.  —  Boil  gently  2  cc.  of  the  pre- 
pared solution  for  two  minutes  with  five  drops  of 
sodium  hydroxide  solution,  five  drops  of  ferrous  sul- 
phate solution,  and  one  drop  of  ferric  chloride  solu- 
tion. Then  add  just  enough  dilute  hydrochloric  acid 
to  dissolve  the  precipitated  ferrous  and  ferric  hydrox- 
ides, and,  if  no  precipitate  appears  at  once,  allow  the 
mixture  to  stand. 

Test  for  Nitrogen  and  Sulphur  when  Present  Together. 
—  Faintly  acidify  1  cc.  of  the  prepared  solution  with 
hydrochloric  acid  and  add  two  or  three  drops  of  ferric 
chloride  solution. 

When  this  test  gives  a  negative  result,  it  does  not  prove  con- 
clusively the  absence  of  sulphur  and  nitrogen,  or  of  either  of  them  ; 
for  the  sodium  sulphocyanate  is  decomposed  by  an  excess  of  so- 
dium into  sodium  sulphide  and  cyanide.  It  is,  nevertheless,  ad- 
visable always  to  try  this  test  when  the  previous  tests  have  shown 
the  presence  of  either  nitrogen  or  sulphur,  since  otherwise  one 
of  these  elements  may  be  overlooked. 

Tests  for  Halogens  when  Sulphur  and  Nitrogen  are 
Both  Absent.  —  Acidify  1  cc.  of  the  prepared  solution 
with  dilute  nitric  acid,  and.  add  a  few  drops  of  silver 
nitrate  solution.  If  a  precipitate  forms,  acidify  a 
larger  portion  with  hydrochloric  acid,  add  a  few  drops 
of  carbon  bisulphide,  and  then  chlorine  water  little  by 


ELEMENTARY  COMPOSITION.  29 

* 

little,  continuing  the  addition,  if  iodine  is  present,  until 
the  violet  color  disappears. 

Test  for  Halogens  when  Either  Sulphur  or  Nitrogen 
is  Present.  —  Acidify  the  remainder  of  the  prepared 
solution  with  dilute  nitric  acid,  and  boil  for  five  min- 
utes in  an  open  vessel  to  expel  hydrogen  sulphide 
and  hydrocyanic  acid.  Filter,  if  necessary,  and  sub- 
ject the  solution  to  the  tests  described  in  the  preced- 
ing paragraph. 

It  is  to  be  remembered  that,  if  sulphocyanate  is  present  in 
the  solution,  a  precipitate  will  be  obtained  with  silver  nitrate, 
whether  halogens  are  present  or  not;  but  the  presence  of  sul- 
phocyanate will  not  affect  the  tests  for  bromine  and  iodine  with 
chlorine  water  and  carbon  bisulphide.  For  the  methods  of  de- 
tecting chlorine  when  the  other  halogens  or  sulphocyanic  acid  is 
present,  Fresenius'  Qualitative  Analysis  may  be  consulted. 


30  ORGAA'IC  LABORATORY  EXPERIMENTS. 

f 

PART   III. 

IDENTIFICATION    AND    SEPARATION    OF    UNKNOWN 
ORGANIC    SUBSTANCES. 

In  identifying  an  unknown  substance,  it  is  first 
desirable  to  determine  whether  it  is  a  pure  chemical 
compound  or  a  mixture.  For  this  purpose  the  melting 
or  boiling-point  is  determined,  special  attention  being 
given  to  the  limits  of  temperature  within  which  a  por- 
tion of  the  substance  melts  or  distills.  A  substance 
which  melts  or  distills  completely  within  1°  or  2°  may 
usually  be  regarded  as  practicably  pure. 

The  usual  qualitative  tests  for  nitrogen,  halogens, 
sulphur,  and  metallic  elements  (Experiment  1)  are  then 
applied  to  the  substance. 

The  behavior  of  the  substance  towards  water,  so- 
dium carbonate  solution,  cold  potassium  hydroxide 
solution,  and  cold  concentrated  sulphuric  acid  (with 
subsequent  addition  of  water),  should  next  be  tested. 
If  the  substance  contains  nitrogen,  its  solubility  in 
dilute  hydrochloric  acid  should  also  be  tried.  Now 
test  for  the  hydroxyl  group  by  means  of  the  sodium 
reaction,  making  sure,  in  case  a  positive  result  is  ob- 
tained, that  it  is  not  due  to  water.  Try  also  the  be- 
havior of  the  substance  towards  bromine  in  carbon 
tetrachloride  solution  ;  and  burn  a  portion  of  it  as 
described  in  Experiment  7. 

Tests  for  all  the  classes  of  compounds  not  excluded 
by  the  results  already  obtained  should  then  be  tried, 
as  many  confirmatory  tests  as  possible  being  made  for 
any  class  apparently  present. 

If  the  substance  is  a  pure  compound,  its  complete 
identification  may  now  be  effected  in  most  cases  by  a 
comparison  of  its  melting  or  boiling-point,  and  other 


IDENTIFICATION  OF  UNKNOWN  SUBSTANCES.      31 

evident  physical  properties,  with  the  corresponding 
properties  of  the  compounds  of  its  class,  which  are 
recorded  in  the  larger  works  on  organic  chemistry 
and  in  the  published  tables  of  melting  and  boiling- 
points  and  other  physical  properties.  After  the.  sub- 
stance is  thought  to  be  identified,  any  special  character- 
istics of  it  described  in  the  text-books  should  be  con- 
firmed. The  following  books  are  recommended  for  pur- 
poses of  reference  :  the  descriptive  works  of  Bernthsen 
or  Richter,  of  Meyer  and  Jacobsen,  and  of  Beilstein ; 
and  the  tables  of  Landolt  and  Bornstein,  of  Bieder- 
mann's  Chemiker  Kalender,  and  of  Carnelley.*  It  is 
well  to  consult  the  smaller  works  first,  since  these 
contain  the  compounds  most  likely  to  be  met  with. 

If  the  substance  is  a  mixture,  it  should  be  sepa- 
rated into  its  components  by  application  of  the  informa- 
tion gained  in  regard  to  it  by  the  qualitative  tests  and 
class  reactions  already  made.  The  separation  should 
be  made  as  nearly  quantitative  as  possible,  so  as  to  de- 
termine the  proportions  of  the  constituents  present. 
The  methods  used  are  almost  always  to  be  based  on 
the  differences  in  solubility  in  some  of  the  various 
solvents,  or  on  the  differences  in  volatility,  either  of 
the  components  themselves  or  of  some  derivative  pre- 
pared from  them.  After  the  substances  have  been 
separated,  they  should  be  purified  by  crystallization, 
distillation,  etc.,  until  a  repetition  of  the  process  causes 
no  further  change  in  their  melting  or  boiling-point. 
Their  identity  may  then  be  fully  established  by  ref- 
erence to  text-books  and  tables  as  described  in  the 
last  paragraph. 


*  Extended  tables  designed  to  lessen  the  labor  involved  in  the  identification  of  pure 
organic  compounds,  by  the  employment  of  a  classification  based  on  differences  in  their 
elementary  composition,  in  their  physical  properties,  and  in  their  chemical  reactions,  are 
in  preparation  by  one  of  the  authors  of  this  book. 


or 
UNIVERSITY 


143 


* 


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